3.2 KiB
[util.smartptr.weak.general]
20 Memory management library [mem]
20.3 Smart pointers [smartptr]
20.3.2 Shared-ownership pointers [util.sharedptr]
20.3.2.3 Class template weak_ptr [util.smartptr.weak]
20.3.2.3.1 General [util.smartptr.weak.general]
The weak_ptr class template stores a weak reference to an object that is already managed by a shared_ptr.
To access the object, aweak_ptr can be converted to a shared_ptr using the member function lock.
namespace std {template class weak_ptr {public:using element_type = remove_extent_t; // [util.smartptr.weak.const], constructorsconstexpr weak_ptr() noexcept; templateconstexpr weak_ptr(const shared_ptr& r) noexcept; constexpr weak_ptr(const weak_ptr& r) noexcept; templateconstexpr weak_ptr(const weak_ptr& r) noexcept; constexpr weak_ptr(weak_ptr&& r) noexcept; templateconstexpr weak_ptr(weak_ptr&& r) noexcept; // [util.smartptr.weak.dest], destructorconstexpr ~weak_ptr(); // [util.smartptr.weak.assign], assignmentconstexpr weak_ptr& operator=(const weak_ptr& r) noexcept; templateconstexpr weak_ptr& operator=(const weak_ptr& r) noexcept; templateconstexpr weak_ptr& operator=(const shared_ptr& r) noexcept; constexpr weak_ptr& operator=(weak_ptr&& r) noexcept; templateconstexpr weak_ptr& operator=(weak_ptr&& r) noexcept; // [util.smartptr.weak.mod], modifiersconstexpr void swap(weak_ptr& r) noexcept; constexpr void reset() noexcept; // [util.smartptr.weak.obs], observersconstexpr long use_count() const noexcept; constexpr bool expired() const noexcept; constexpr shared_ptr lock() const noexcept; templateconstexpr bool owner_before(const shared_ptr& b) const noexcept; templateconstexpr bool owner_before(const weak_ptr& b) const noexcept; size_t owner_hash() const noexcept; templateconstexpr bool owner_equal(const shared_ptr& b) const noexcept; templateconstexpr bool owner_equal(const weak_ptr& b) const noexcept; }; template weak_ptr(shared_ptr) -> weak_ptr;}
Specializations of weak_ptr shall be Cpp17CopyConstructible andCpp17CopyAssignable, allowing their use in standard containers.
The template parameter T of weak_ptr may be an incomplete type.